a matter of course
An action or result that is expected or logical. Handshakes are usually a matter of course after an initial meeting between two people.
matter of course, a
Something that is expected, as in It was a matter of course that police officers received special training. It is also put as as a matter of course, meaning "as part of a standard procedure," as in The employer checked John's references as a matter of course. First recorded only in 1809, this idiom uses course in the sense of "the natural or logical order of events."